Kill user session after X11 inactivity, prototype version

display-manager-killer.service

[Unit]
Description=KILL_DISPLAY_SESSION_ON_IDLE
After=display-manager.service

[Service]

Environment=DISPLAY=:0
WorkingDirectory=/home/display/
Type=simple
ExecStart=/usr/sbin/idlekillr display
Restart=always
RestartSec=5
StandardOutput=syslog+console
TimeoutStartSec=5
StandardError=syslog

[Install]
WantedBy=display-manager.service

xidlekillr.py

#!/usr/bin/env python3
import subprocess
from subprocess import call

import syslog
import time,os
import sys
assert sys.argv[1]
MAXT=os.getenv("KILL_TIME") or 10
DEVNULL=open("/dev/null",'wb')
def getIdleSec():
        try:
                ret = subprocess.check_output("xprintidle",stderr=DEVNULL)
                ret = int(ret)/1000
                return ret
        except subprocess.CalledProcessError as e:
                return
        except ValueError as e:
                return

def log(str):
        print(str)
        #syslog.syslog(str)

log("Running idlekillr")
def run():
                while True:
                        prev = getIdleSec()
                        if prev and prev>1:
                                break
                        time.sleep(0.5)

                initial=True
                last=time.time()
                log("started tracking")

                while True:
                                time.sleep(2.3)
                                now=time.time()
                                cur = getIdleSec()
                                if not cur:
                                        log("Lost screen, restarting")
                                        break

                                if cur-prev<0: # triggered
                                                initial=False
                                                last=now
                                                log("triggered")

                                prev=cur

                                if not initial and (now-last)>MAXT:
                                                log("killtime")
                                                call(["/usr/bin/killall","-3","-u",sys.argv[1]])
                                                call(["/etc/init.d/nodm","stop"])
                                                call(["/usr/bin/killall","-9","-u",sys.argv[1]])
                                                call(["/etc/init.d/nodm","start"])
                                                break


while True:
        run()
        time.sleep(0.1)